Methods of and apparatus for hydrostatic forming

ABSTRACT

Deforming of a workpiece wherein a workpiece is clamped between high friction and low friction surfaces and frictional forces are utilized to transport the workpiece over the low friction surface and into engagement with a die surface. Further, the forming of a projection, in particular a flange, on a plastically deformable member by flaring a portion of the member and by building up hydrostatic pressure in the member, including the flared portion, sufficiently high to place the member in a plastic state and cause a portion of the member, including the flared portion, to flow and increase in thickness thereby forming the projection. The hydrostatic pressure is built up in the member by the application of hydrostatic pressure from a pressurized fluid medium, or by the mechanical application of pressures.

United States Patent Fuchs, Jr. 1 Aug. 29, 1972 [54] METHODS OF AND APPARATUS FOR 2,877,675 3/1959 Corbefls ..'....72/354 HYDROSTATIC FORMING 3,172,928 3/ 1965 Johnson..... ..72/60 3,205,689 9/1965 Joseph ..72/ 146 [72] Invent Fuchs Pmcemn 3,286,498 11/1966 Cogan ..72/60 3,287,948 11/1966 Alexander et a1. ..72/57 [73] Assignee: Western Electric Company, Incorporated, New York, NY. FOREIGN PATEN IS OR APPLICATIONS [22] I Filed: March 20, 1968 645,773 9/ 1962 Italy ..72/60 625,011 6/1949 Great Britain ..72/349 [21] 7225 737,411 9/1955 Great Britain ..72/265 Related us. Application Data Pr E R1 h M H b ima xaminer 'c at er st [63] goiictlgisuaroanl-(iirgrpst of Ser. No. 461,250, June g, Schuman 52 us. 01. ..72/60, 72/370, 29/421 [57] ABSTRACT 1 [51] Int. Cl. ..B2l d 19/00 Deforming of a workpiece wherein a workpiece is [58] Field of Search ..72/370, 54, 56, 60-62, clamped between high friction and low friction sur 72/58, 253, 264, 266, 667, 384, 367, 354; faces and frictional forces are utilized to transport the 29/421 workpiece over the low friction surface and into engagement with a die surface. Further, the forming of a [56] References Cited P ojection, in particular a flange, on a plastically deformable member by flaring a portion of the UNITED STATES PATENTS member and by building up hydrostatic pressure in the 4,525,599 5/1891 Dooley ..l8/30 member, including the flared portion, sufficiently high 524,504 8/ l 894 Robertson ..72/60 to place the member in a plastic state and cause a por- 524,506 8/ 1894 Robertson ..72/60 i f th member, including the flared portion, to 524,509 8/1894 Robertson ..72/60 flow and increase in thickness thereby forming the projection The hydrostatic pressure is built up in the 2,157,044 5/1939 Wendel ..72/60 member by the i i f hydrostatic pressure g g d a1 from a pressurized fluid medium, or by the mechanical 0m 6 a 2,375,574 5/1945 Metheny et a1 ..29/520 pp 1 p 2,743,691 5/ 1956 Cuq ..72/60 18 Claims, 13 Drawing Figures gb is 72- 5 20- /9 1 i ii 42 l 26 I l\ -52 5 I 1 1,\

HYDRAULIC PUMP L \30 L sun/PH PAIENTEflwczs m2 SHEET 1 0F 5 FIG.

A TTORNEY PAIENTED AUG 29 I972 SHEET 2 OF 5 I I I I I I I I l I iIlinIIImIzItL IIII faa

HYDRAULIC PUMP SUMP

PAIENTEBwsee m2 SHEET 3 UP 5 HYDRAULIC PUMP PATENTED M1829 m2 SHEET 5 [1F 5 FREE- BODY OF WORKPIECE FREE-BODY OF PRESSURE SLEEVE FIG. (2

METHODS OF AND APPARATUS FOR HYDROSTATIC FORMING CROSS REFERENCESTO RELATED APPLICATIONS This is a continuation-in-part of my copending application, Ser. No. 461,250, filed June 4, 1965, now aban-. doned, which relates to METHODS OF AND AP- PARATUS FOR l-IYDROSTATIC EXTRUSION.

BACKGROUND OF THE INVENTION This invention relates to methods of and apparatus for the forming of projections on plastically deformable material, and more particularly, to methods of and apparatus for the forming of a flange on an end of a tubular member by extruding a flange thereon by building up hydrostatic pressure in the tubular member sufficiently high such that the tubular member is in a plastic state.

Lengths of tubular members, such as for example, wave guides, are typically joined together by mechanically interlocking flanges formed on the ends of the tubular members. Generally, the flanges are bolted together, however, welding or brazing is sometimes used.

Due to the ever increasing usage of tubular members, such as the aforementioned wave guides, it has become increasingly desirable, if not economically necessary, to be able to provide such tubular members with structurally sound flanges in an inexpensive manner, and, perhaps even more importantly, to be able to provide such flanges in a manner which may be performed by machine operation.

In the past, flanges have been formed on tubular members in many different and varied ways. Such ways have included the well-known spinning and flaring operations which have the ever attendant limitation of being able to form flanges of only very limited thickness vis-a-vis the wall thickness of the tubular member itself; the thickness of a flange formed by the spinning or flaring operations being invariably less than the original wall thickness of the tubular member itself. Furthermore, the greater theouter diameter of a flange formed by the spinning or flaring operation, the more thin the flange so formed becomes.

Cold extrusion techniques have also been employed in the past to form flanges on tubular members. Such extrusion techniques have not proven to be altogether satisfactory and virtually all such prior art cold extrusion techniques, whether or not they satisfy the flange thickness requirement, have the nearly always fatal problem of radial fracture in regard to the extrusion of a flange of the outer diameter usually desired.

Research conducted in an eflort to provide economically feasible methods of and apparatus for forming structurally sound flanges on tubular members, indicates that such flanges can be formed, or extruded, if the tubular member can be placed in a plastic state, and maintained in such a plastic state, while a flange is being extruded on the tubular member.

More specifically it has been discovered that the flanges of the desired thickness and outer diameter can be extruded on tubular members by building up hydrostatic pressure in the material comprising the tubular member (usually metal and generally copper in the instance of wave guides) sufficiently high so as to place such material in a plastically deformable state, and extruding the material into an expandable, or variablesized, die cavity, while maintaining the material in such hydrostatic pressure. Such techniques provide extruded flanges of a thickness, outer diameter and structural soundness, never before achievable.

Research has indicated that, prior to the building up of such hydrostatic pressure within the tubular member, it is desirable to first flare the end portion of the tubular member on which the flange is to be formed, outwardly into the expandable or variablesized die cavity. Such flaring assists in achieving the desired initial flow of the material comprising the tubular member into the die cavity.

Further, with regard to the prior art flange extrusion techniques, difficulty has been encountered in maintaining an even or uniform flow of the flange forming material being extruded into all the areas of an extrusion die cavity which defines the flange.

Research directed toward a solution of this difficulty has resulted in the invention of a self-balancing die which assists in providing a uniform or even extrusion of the flange forming material into all areas of a die cavity which defined the shape and size of the flange to be extruded.

The present invention further relates to the utilization of friction extrusion to form a flange on a tubular member.

Most of the prior art methods and apparatus for flange forming have their greatest utility in the forming of flanges on comparatively short lengths of tubular members. Frequently, it is highly desirable, if not economically necessary, to have apparatus for forming flanges on tubular members of comparatively great length. In the operation of most of the prior art flange forming apparatus, the member on which the flange is to be formed must be insertable entirely within the apparatus. More specifically, in the fluid extrusion apparatus known to the prior art, the tubular member on which a flange is to be formed must be insertable, in its entirely, within a fluid pressure: chamber, or else, elaborate fluid sealing techniques and devices must be employed to provide the desired fluid seal about a length of tubular member extending out of such a fluid pressure chamber. Furthermore, if a split die is used with such fluid forming apparatus, the fluid will invariably escape through the split die and present a highly undesirable problem.

Additionally, in many present day fluid extrusion techniques, the fluid pressure utilized is frequently at a pressure of several hundred thousand pounds per square inch, and at such pressures, many fluids typically utilized in a fluid extrusion operation, solidify and hence obtaining additional fluid pressure is precluded.

Accordingly, in view of the foregoing, it is highly desirable to be able to form flanges on tubular members, for example, without the use of a pressure forming fluid, and wherein the pressure exerted on the tubular member on which a flange is to be formed, is sufficiently high such that hydrostatic pressure is built up in the tubular member so as to place the member in a plastic state. The friction extrusion apparatus of the present invention provides such a result.

Accordingly, it is the general object of this invention to provide novel methods and apparatus for forming workpieces in a pressure environment.

Also, it is an object of the present invention to provide novel methods of and apparatus for forming projections, especially flanges, on a plastically deformable member.

Another object of the present invention is to provide new and improved methods of and apparatus for extruding a flange on an end of a tubular member by building up hydrostatic pressure in the material comprising the tubular member sufficiently high to place the material in a plastic state, and extruding such material into an extrusion die cavity, while maintaining the material in the plastic state.

A still further object of the present invention is the provision of a self-balancing die for providing an even or uniform extrusion of the flange forming material into all the areas of an extrusion die cavity.

Another object of the present invention is to provide new and improved friction extrusion apparatus for forming a flange on a tubular member.

Another object of the present invention is to provide new and improved apparatus for forming a flange on a tubular member of comparatively long length.

Another object of the present invention is to provide new and improved apparatus for forming a flange on a tubular member utilizing friction extrusion, wherein the pressure providing the frictional force on the tubular member is developed in a force gradient applied along a portion of a length of tubular member.

Still a further object of the present invention is to provide new and improved apparatus for forming a flange on a tubular member wherein friction extrusion is employed in conjunction with an expandable die cavity and a movable back-up die to build up hydrostatic pressure in the tubular member sufficiently high so as to place the tubular member in a plastic state.

A feature of the present invention is a method for forming a projection on a plastically deformable member, including the steps of flaring a portion of the member, building up hydrostatic pressure in the member sufficiently high to place the member in a plastic state, and allowing the flared portion to increase in thickness while maintaining the member in such hydrostatic pressure.

Another feature of the present invention is to provision of apparatus for forming a projection on a plastically deformable member, which includes means for flaring a portion of the member, and means for building up and maintaining hydrostatic pressure in the member, including the flared portion, sufficiently high to place the member in a plastic state and for allowing the flared portion to increase in thickness.

Still another feature of the present invention isthe provision of a variable-sized extrusion die cavity whose size is variable in accordance with the flow pattern of or the hydrostatic pressure in, the material being extruded into such cavity.

A still further feature of the present invention is the provision of a self-balancing, back-up die for maintaining an even and uniform extrusion of flange forming material into an extrusion die cavity.

Another feature of the present invention is the provision of an apparatus for extruding a flange on a tubular member which includes low friction means for engagement with the tubular member, forcing means for forcing said low friction means into high pressure, low friction engagement with the tubular member, high friction means insertable within the tubular member, and means for operating the forcing means and for operating the high friction means to pull the tubular member frictionally through a die orifice and extrude portions of the tubular member into a die cavity to form a flange.

BRIEF DESCRIPTION OF THE DRAWING An even more complete understanding of the present invention may be gained from the following detailed description when read in conjunction with the appended drawings, wherein:

FIG. 1 is a primarily diagrammatic representation, partly in section, showing apparatus for practicing the present invention;

FIG. 2 is a partial view, taken from FIG. 1, showing the initial flaring of the end of a tubular member outwardly into an expandable die cavity;

FIG. 3 is substantially the same as FIG. 1, but showing a self-balancing, back-up die;

FIGS. 4, 5, 6 and 7 are transitional, diagrammatic representations, in section, showing the manner in which the flange formed on the tubular member in accordance with this invention increases in thickness and outer diameter;

FIG. 8 is a diagrammatic representation, partially in section, of friction extrusion apparatus for practicing the present invention;

FIG. 9 is an exploded view of certain structural elements of FIG. 8 shown in greater detail; and

FIG. 10 is a composite view illustrating the relationship between radial pressure applied to a workpiece and the axial stress developed in the workpiece during a forming operation; and

FIGS. 11-13 are diagrammatic views of a pressure sleeve and workpiece illustrating the structural design relationships between the workpiece and the pressure sleeve.

DETAILED DESCRIPTION Referring now to FIG. 1, there is shown a high-pressure vessel 10 having a fluid filled pressure chamber 12 formed therein. Extendable into the pressure chamber is a combination piston 14 and mandrel 16. A high pressure seal 18 encircles the piston 14 and prevents the escape of fluid upwardly out of the pressure chamber upon the pressure in the chamber being increased due to the further entry of the piston 14 into the pressure chamber.

The seal 18 may be one of several such pressure seals known in the art and could be, for example, made of Teflon whose plastic and low friction qualities as well known to those skilled in the art.

The lower portion of the high pressure vessel 10 is provided with inwardly projecting shoulder portions 19 which define an extrusion die, indicated by the general numerical designation 20, and a die orifice 22. The diameter of the extrusion die orifice is slightly smaller than the outer diameter of the tubular member 24 on which the flange 26 is to be formed; the die orifice in one embodiment of the present invention providing approximately 5% interference with the passage therethrough of the tubular member 24.

While the extrusion die 20 shown in FIG. 1 is integral with the high pressure vessel 10, it will be understood by those skilled in the art that in many embodiments it may be desirable to provide physically separable extrusion dies which would be detachably secured in the bottom of the pressure chamber 12, and which may be of various sizes to accommodate the extrusion of flanges onto various sized tubular members.

The high pressure vessel is seated on, and detachably secured to, such as by threaded engagement or bolts (not shown), a base member or hydraulic cylinder 30. The cylinder 30 is provided with an irregularly shaped centrally formed chamber 32 which is partially filled with hydraulic fluid 34. A back-up die 38 is supported hydraulically on the fluid 34, and the lower portion of the back-up die is encircled by a high pressure seal 40 similar to the previously described high pressure seal 18. I

The back-up die 38 is provided with a die surface 42 and a centrally formed, substantially frusto-conically shaped bore 44 for receiving the mandrel l6.

Closely encircling the upper portion of the back-up die 38 is an annular member 46 residing in a counterbore 48 formed in the upper portion of the cylinder 30. The annular member 46 is received slidably within the counterbore 48 for lateral movement therein.

The extrusion die 20, the back-up die 38, and the annular member 46, formcooperatively an expandable,

or variable-sized, extrusion die cavity into which the flange 26 is to be extruded.

Due to the fact that the wall thickness of virtually all commercially available tubular members, such as wave guides, varies along the length of such tubular members, back-up die 38 and annular member 46 are mounted for slight lateral movement, as shown in FIG. 1, to accommodate for such variation in the wall thickness of such tubular members, and to maintain the mandrel 16 in substantially central location of the central bore 44 formed in the back-up die.

Referring now primarily to FIG. 2, the initial upward position of the back-up die 38 is shown relative to the extrusion die 20. It has been found that desirable results are achieved by initially positioning the back-up die 38 opposite the extrusion die such that they are separated by a distance no more than approximately l- :5 of the wall thickness of the tubular member to be extruded. This positioning of the back-up die 38 is achieved by the provision of shoulders 52, FIG. 1,

formed integrally with the cylinder 30, and shoulders 54 formed integrally with the back-up die 38; the firstly mentioned shoulders being engageable by the secondly mentioned shoulders to limit the upward movement of the back-up die 38. t

The backup die 38 is urged upwardly by the hydraulic pressure developed within the fluid 34 by a hydraulic pump 60 which is in communication with the fluid through an adjustable relief valve 62. The hydraulic pump 60 draws fluid from a fluid supply or sump 63 which is in communication with the relief valve 62.

It will be understood by those skilled in the art, that the structure of FIGS. 1 and 2 is merely a diagrammatic representation of structure illustrative of the present invention. Further, it will be understood that the present invention can be utilized to form flanges on tubular members irrespective of the cross-sectional configuration of the tubular member. The external configuration of the mandrel 16 is complementary to the internal 6 configuration of the tubular member, the configuration of the die orifice 22 is complementary to the external configuration of the tubular member, and the internal configuration of the annular member 46 and the configuration of the back-up die surface 42 are complementary to the desired size and shape of the flange to be formed. Thus, flanges can be formed on round rectangular, etc., shaped tubular members.

OPERATION (FIGS. 1 AND 2) The practice of the present invention with the apparatus of FIGS. 1 and 2 is carried out in the following manner. High pressure vessel 10 is separated from the hydraulic cylinder 30 and the mandrel 16 is inserted within the tubular member 24, the end of which is shaped as shown in FIG. 4. The high pressure vessel 10 is then secured to the hydraulic cylinder 30, as described infra, and the pressure chamber 12 is filled with hydraulic fluid.

The back-up die 38 is positioned, as described above and as shown in FIG. 2, the proper distance from the extrusion die 20, as described above. The piston 14 is then forced downwardly, by suitable means not shown, into the pressure chamber 12 and displaces its volume within the fluid occupying the pressure chamber. The length of travel of the piston 14 is predetermined so as to raise the pressure of the fluid to a level sufficiently high such that the force components of the fluid pressure indicated by numerical designation 64, acting longitudinally on the tubular member 24, force the mandrel supported tubular member 24 downwardly through the extrusion die orifice 22 into engagement with the die surface 42 of the back-up die 38. Upon engagement with the die surface 42 the end of the tubular member 24 is flared outwardly into the variable-sized die cavity as shown in FIGS. 2 and S.

The length of travel of the piston 14 is also predetermined so that component forces 64 are sufficient, in cooperation with the back-up die 38, to build up hydrostatic pressure in the tubular member 24, including the flared portion, sufficiently high so as to place the tubular member, including the flared portion in a plastic state.

Further entry of the piston 14 into the pressure chamber, increases the hydrostatic pressure in the tubular member 24, and in particular in the flared portion within the expandable extension die cavity.

The back-up die 38, in response to the increased hydrostatic pressure within the portion of the tubular member occupying the die cavity, or viewed differently, in response to the flow pattern of the metal within the die cavity, will tend to move downwardly, away from the extrusion die 20. The relief valve 62 is adjusted so that pressure within the fluid 34 will be re lieved in response to the compressional forces applied to the fluid by the back-up die 38 tending to move downward, and the back-up die will be allowed to move downwardly such that the hydrostatic pressure in the tubular member, including the portion within the die cavity, will be maintained at a level sufficiently high so as to maintain the tubular member, including the portion within the die cavity, in a plastic state. More specifically, when the pressure within the fluid 34 exceeds a predetermined limit, the relief valve 62 will relieve the excess pressure by diverting a portion of the fluid into the fluid supply or sump 63. Thus, relieving the pressure within the fluid 34 permits the back-up die 38 to move downwardly, yet the pressure remains sufficiently high so as to maintain, in cooperation with fluid force components 64, the tubular member, including the portion within the die cavity, in a plastic state.

The fluid component forces 64 will force successive portions of the tubular member through the die orifice 22 into the extension die cavity which portions accumulate with the initially flared portion of the tubular member. This accumulation of material within the expandable extension die cavity, increases in thickness, due to the aforementioned back-up die operation, and will also flow outwardly against the annular member 46, to form the flange 70 of the desired thickness t and outer diameter OD. shown in FIG. 7. FIGS. 5, 6 and 7 show this transitional extrusion, or growth of the flange.

It will be understood by those skilled in the art, that the step-by-step description of the downward movement of the piston 14, was merely for convenience of presentation and that in actual practice, the movement of the piston is one continuous, smooth stroke.

Referring again to FIG. 1 the component forces, of the fluid pressure within the chamber 12, indicated generally by the arrows 72, act normally on the walls of the tubular member 24 and prevent the walls from buckling or rippling by maintaining the walls against the mandrel 16.

With one embodiment of the apparatus shown in FIG. 1, a flange was extruded on a tubular member 0.625 inch in outer diameter and 0.0,225 inch in wall thickness. The flange extruded by the use of such apparatus measured 0.160 inch in thickness,- and 1.048 inches in outer diameter. It will be noted that the flange thickness was over seven (7) times that of the original wall thickness, and the outer diameter was over 67 percent greater than the original outer diameter of the tubular members. The extrusion pressure was 500,000 p.s.1.

Self-Balancing Back-Up Die It has been found that, due to the previously mentioned variation in the wall thickness of commercially available tubular members, such members do not always extrude evenly or uniformly into the variablesized die cavity. Accordingly, it has been found necessary to provide a self-balancing, back-up die for accommodating such variation in tubular member wall thickness.

Referring now to FIG. 3, there is shown a self-balancing, back-up die 38 comprised of a ball member 80 mounted pivotably in a socket member 82. The ball member 80, similar to the back-up die 38 of FIG. 1, is provided with the die surface 42 and the centrally formed, substantially frusto-conical shaped bore 44 for receiving the mandrel 16. The remainder of the structure shown in FIG. 3 is the same as the corresponding structure of FIG. 1.

In the event that the material comprising the tubular member flows into the variable-sized die cavity in an uneven rate, i.e., metal is being extruded into one area of the die cavity at a rate greater than the rate at which the metal is being extruded into other areas of the die cavity, pressure will be greater on the surface of the back-up die in the area of the greater rate of extrusion. This unbalanced pressure will pivot the ball member within the socket member 82 toward the direction of excessive accumulation. Such pivoting of the ball member will move the mandrel 16 within the die orifice 22 toward the direction of excessive accumulation and such mandrel movement will thereby reduce the spacing between the mandrel 16 and the die orifice 22 and retard the extrusion of the metal into the area of excessive accumulation. Otherwise, the self-balancing, backup die of FIG. 3 functions in the same manner as the previously described back-up die shown in FIG. 1.

In one embodiment of the self-balancing, back-up die shown in FIG. 3, the ball member 80 is formed of beryllium copper with an indium coating, and the socket member 82 is of Teflon.

FRICTION EXTRUSION The term friction extrusion as used herein, and in appended claims, involves a technique of utilizing frictional forces to pull a member, such as a tubular member, through an extrusion die orifice, rather than the utilization of forces, such as fluid forces, to push such a member through an extrusion die orifice.

Referring now to FIG. 8, there is shown a comparatively long length of tubular member 24 on which is to be formed a flange indicated generally by the numerical designation 26. Encircling the tubular member 24 is a low friction, pressure sleeve indicated by the general numerical designation 1 14, and comprised of a tapered annular portion 117 and an untapered annular portion 118. The low friction, pressure sleeve may be comprises of two parts as shown, for convenience of manufacture, or may be made of one integral piece of the same general configuration of both annular members.

Encircling a portion of the tubular member 24, and the tapered collar 117 of the low friction, pressure sleeve 114, is a forcing member, or circular piston or plunger having a central bore formed therein. The lower portion of the forcing member 120, as shown in cross section, is of a conical-tapered configuration. The tapered configuration of the forcing member 120 is complementary to the tapered annular low friction, pressure member 117. The forcing member 120 may be provided with serrations or teeth 12], providing a more positive gripping or constrictive action between the forcing member and the pressure sleeve 114.

The annularly shaped, low friction, pressure sleeve 118 is for encircling tightly, yet slidably, the tubular member 24 so as to create a high pressure, low friction engagement between the sleeve and the tubular member. The sleeve is comprised of a material which is resilient and deformable and whose surface is very slick or frictionless, so as to provide a high pressure, low friction engagement with the tubular member 24. It has been found that Teflon possesses these desired characteristics, and that low friction, high pressure sleeves made of Teflon work in a satisfactory manner.

The forcing member 120 encircles a portion of the tubular member 24 and the tapered portion, described above, encircles, in a close complementary relationship, the tapered annular portion 117 of the pressure sleeve 114. The end of the forcing member engages the untapered annular portion 118 of the pressure sleeve 114. Thus, as the member 120 is forced downwardly,

the low friction, high pressure sleeve 114 be forced or squeezed into a high pressure engagement with the tubular member 24, but since the sleeve is made of a slick material, such as the aforementioned Teflon, there will be a low friction engagement between the annular sleeve 1 14 and the tubular member. Accordingly, the tubular member may slide easily internally of the low friction, high-pressure sleeve 1 14.

The exterior of the mandrel 16 is provided with a conventionally rough, high friction surface. The mandrel, as shown in FIG. 8, is insertable within the tubular member 24, and when the forcing member 120 forces, or squeezes, the sleeve 114 into engagement between the surface of the mandrel 16 and the interior of the tubular member is so much greater than the frictional forces between the exterior of the tubular member and the interior of the annular pressure sleeve 114, that the mandrel pulls the tubular member downwardly through the extrusion die 20 when the mandrel is forced downwardly.

Referring again to the tapered complementary configuration of the low friction, high-pressure sleeve 114, such tapered configuration provides for the development of a pressure gradient along the length of the tapered annular sleeve 117. The pressure gradient increases as the tapered portion of the sleeve 117 increases in thickness. This pressure gradient prevents the otherwise abrupt application of high pressure to the tubular member 24 which could apply such localized or abrupt constrictive or squeezing force sufficient to actually squeeze the tubular member in two.

The squeezing of the tubular member in two, or member pinch-off, occurs when at any point of engagement between the tubular member and the sleeve 114, the radial pressure applied to the tubular member by the sleeve 114 exceeds the axial stress produced in the tubular member by the frictional pulling forces developed between the mandrel 16 and the tubular member 24, by an amount greater than the yield strength of the material. Pinch-off also occurs when such axial stress produced in the tubular member at any point, is greater than or less than, such radial pressure applied by the sleeve 114 at the samepoint, by an amount equal to the yield strength of the tubular member.

A pressure plate 130 is provided with a centrally formed bore 138 and is secured to the annular member 124 by long threaded fasteners 132. A portion of the underside of the pressure plate 130 engages the forcing member 120 and forces the member downwardly into engagement with the low friction, high pressure sleeve 114. Thus, the pressure plate 130 preloads the forcing member 120.

A pressure collar 136 resides within the centrally formed bore 138, and downwardly acting forces from some suitable source not shown, represented by arrows 139, force the collar downwardly into engagement with the forcing member 120 with sufficient force to cause the forcing member 120 and sleeve 114 to function as described above.

The annular member 122 is maintained in pressure contact with the annular member 124 by a plurality of threaded members 142 extending through the pressure plate 130 and into engagement with the upper end of the annular member 122. The threaded member 142 keeps the annular member 122 from riding upwardly in response to back pressure generated within the expandable die cavity.

The annular member 124 is in threaded engagement with a bore member or hydraulic cylinder 150 which is provided with a partially filled fluid chamber 152. Residing within the fluid chamber 152 is a hydraulic piston 154 which comprises, in cooperation with a retaining ring 156 and a facing die 158, a back-up die indicated generally by the numerical designation 160. The back-up die 160 is the counterpart of the back-up die 38 of FIG. 1.

OPERATION (FIGS. 8 AND 9) It will be assumed that the tubular member 24 and the structural elements of the apparatus occupy the positions shown in FIG. 8. The forcing member has been preloaded by the action of the pressure plate and the long threaded fasteners 132.

The mandrel 16 has been inserted within the tubular member 24, and is forced downwardly by a force, from some suitable source not shown, represented by the arrow 165. The sleeve 114, as described above, forces, or squeezes, the tubular member 24 into a high friction engagement with the surface of the mandrel such that the mandrel pulls the tubular member 24 downwardly, sliding easily within the sleeve 1 14, into the expandable die cavity.

Forces indicated by arrow 139 force the pressure collar 136 downwardly into engagement with the foreing member 120 which, in turn, forces the sleeve 114 into a low friction, high pressure engagement with the tubular member 24. 1

The mandrel pulls the tubular member downwardly with such force that the end of the tubular member upon engaging the surface of the back-up die, is flared outwardly into the die cavity, and. the pulling force of the mandrel, in cooperation with the back-up die 160, builds up hydrostatic pressure in the tubular member sufiiciently high such that the tubular member, and the flared portion within the die cavity, are placed in a plastic state.

The remaining action of the back-up die in the formation of the flange 26, is substantially the same as the above-described action of the back-up die 38 of FIG. 1.

Referring again to FIG. 8, it will be noted that only a small portion of the tubular member 24 is confined within the flange forming apparatus and that the tubular member 24 may be of comparatively long length as it may extend upwardly out of the apparatus any reasonable distance. Also, it will be noted that no fluid chamber is employed in confining the tubular member and hence no difficult fluid sealing problems are encountered.

Referring again to the aforementioned pressure gradient provided by the high pressure sleeve 114 and the aforementioned consideration of tubular member or workpiece pinch-off, attention is now directed to FIG. 10 which includes substantially one-half of a cross-sectional view of the mandrel l6; and the generally annular workpiece 24, pressure sleeve 114, and forcing member or punch 120.. The pressure sleeve 114 is shown not as having a tapered portion 117 as in FIGS. 8 and 9, but rather the corresponding portion 117 is shown as being of rectangular cross-section. Such rectangular cross-sectional portion provides a pressure gradient as shown in FIG. 10, and being of rectangular cross-section, is more readily, and less expensively, produced.

Generally the cross-sectional view of FIG. further illustrates, diagrammatically, the above-described mechanical pressurization of the workpiece or tubular member, and the frictional transport or advancement of the workpiece by the mandrel 16 into engagement of the die surface 158 to flare the workpiece and build up hydrostatic pressure in the workpiece sufficiently high such that the workpiece, including the flared portion, is placed in a plastic state, in the manner described in detail above.

As mentioned above, the high pressure sleeve 114 is loaded (pressurized) by forces 139 (FIG. 8) which through collar 136 and forcing member 120, force the sleeve 114 into low friction, high pressure engagement with the tubular member 24. As forces 139 are exerted on the high pressure sleeve 114 of FIG. 10, and since the sleeve 114 is confined by the annular member 122 (also see FIG. 8) and the forcing member 120, the sleeve, being comprised for example of Teflon as taught above, will become loaded, i.e., pressurized to an amount P, and hence, will exert radial pressure P against the portion of the tubular member or workpiece 24 extending adjacent to the enlarged annular portion 118 of the pressure sleeve 114. The pressurized sleeve material (e.g., Teflon), in particular theenlarged portion, being under pressure, will tend or attempt to flow into the relatively narrow and elongated space between the workpiece 24 and the forcing member 120, i.e., the space occupied by the pressure sleeve portion 117. The pressurized sleeve material (e.g., Teflon) will encounter resistance upon its attempt to enter into such space, and hence the pressure P will drop from an amount P at point E, to an amount P, at point G. Thus, a radial pressure profile, as shown in the graph of FIG. 10, will be provided along the overall length of the pressure sleeve 114, which profile will include a radial pressure gradient along the length L of the pressure sleeve in addition to the substantially linear pressure P provided along the length L of the sleeve 114. This radial pressure will apply radial pressure to the workpiece or tubular member 24 to force the workpiece into high friction and high pressure engagement with the mandrel 16; it being understood, that the frictional forces F m applied to the workpiece or tubular member 24 by the mandrel, for the advancement of the workpiece, is a function of the radial pressure applied to the workpiece by the pressurized pressure sleeve 1 14.

Upon the workpiece being placed in hydrostatic pressure as described above, axial stress S A is produced in the workpiece in the portion forming the flange 26 and also in the successive portions of the workpiece advancing past the pressure sleeve 114 to form the flange 26.

It will be understood that at any point of the workpiece opposite the pressure sleeve 114, the radial pressure applied to the workpiece at such point, cannot exceed the axial stress in the workpiece at that point, by an amount greater than the yield strength of the workpiece, or else the workpiece pinch-ofi will occur. Similarly, it will be understood that the axial stress, at

any point in the workpiece adjacent the pressure sleeve, cannot exceed or fall below the applied radial pressure at that point, by a respective amount greater or less than the yield strength of the workpiece material, or else workpiece buckling will occur.

These required relative conditions between the radial pressure and axial stress (which could be either above or below the radial pressure as indicated by the two profiles so identified) are indicated in the graph of FIG. 10. More specifically, it will be understood, that the axial stress profiles cannot depart from the radial pressure profile, in the vertical direction along the ordinate, by an amount greater than the yield strength of the workpiece material; the vertical distances between the arrows A and B being indicative of the yield strength of the workpiece material.

These axial stress and radial pressure relationships at any point in the workpiece adjacent the pressure sleeve 114 can be further appreciated by reference to the representative cube of workpiece material C (FIG. 10) taken at any such point in the workpiece. The arrow P and its opposed arrow in dashed outline indicating the opposed reactive radial pressure, represent the radial pressure applied to the workpiece at any point; and the arrow 8,, and its opposed arrow in dashed outline indicating the opposed reactive axial stress, represent the axial stress in the workpiece at the same point. (It being understood that the hoop stress, which is present, can be neglected for this consideration since the workpiece at this point is a continuous annulus, and, at the pressure levels involved, the workpiece is self supporting.) Thus upon attention to the cube C, it will be noted that the general relationship between such axial stress and radial pressure, is such that neither can depart from the other by an amount greater than the yield strength of the workpiece, or else workpiece pinch-off or buckling will occur.

In view of the above, and referring again to the graph of FIG. 10, it will be understood that since the axial stress (considering the lower profile) in the workpiece produced by the frictional forces F m are zero at point G, the value of the radial pressure gradient at point G cannot be in excess of the yield strength of the workpiece material. Thus since the radial pressure P produced in the enlarged portion 118 of the pressure sleeve 114 would be in the order of 200,000 psi to provide a flange of twice the diameter and nine (9) times the thickness on a copper workpiece having a yield strength of approximately 10,000 psi; it will be understood, that the length L of the portion 117 of the pressure sleeve 114, must be sufficiently long to drop the radial pressure to an amount not in excess of the yield strength of the workpiece.

It will be further understood that the length of the workpiece to which the radial pressure is applied, i.e., the length of the workpiece adjacent the pressure sleeve 114, must be of sufficient length that the frictional forces F which forces are a function of such workpiece length, are sufficiently great to force the workpiece into engagement with the die surface 158 to produce the above-described plastic state in the workpiece.

Referring now to FIGS. 11 and 12, a manner of determining the lengths L and L will be set forth in detail.

Referring first to FIG. 11, there is shown a free body of that portion of the workpiece 24 in contact with the pressure sleeve 114; only a partial cross-sectional view of the workpiece being shown in solid outline and a partial cross-sectional view of the pressure sleeve 114 being shown in dashed outline, it being understood that both such members are complete annular members as indicated in FIGS. 8 and 9. The summation of forces acting on the free body is expressed by the following equation:

m o)/( 1 f where:

S A axial stress in workpiece required for forming operation.

D outside diameter of tubular workpiece.

d inside diameter of tubular workpiece.

P radial pressure applied to workpiece by pressure sleeve (ideally pressure required to place workpiece in plastic state).

L length of enlarged portion of pressure sleeve.

L length of reduced thickness portion of pressure sleeve.

f,,, coefficient of friction between workpiece and mandrel.

f, coefficient of friction between workpiece and the pressure sleeve.

Referring again to equation (1), the term to the left of the equal sign represents the forces acting to the right on the free body workpiece which are produced by the axial stress S acting against the annular area of the workpiece 24. The first two terms to the right of the equal sign are the frictional forces acting to the left on the free body workpieceand are, respectively, the frictional forces F applied to the interior surface of the workpiece by the mandrel 16 along the lengths L and L respectively. The second two terms to the right of the equal sign are the frictional forces F acting to the right on the workpieceand are, respectively, the frictional forces applied to the exterior surface of the workpiece by the pressurized pressure sleeve 114 along the lengths L and L respectively. It will be noted that the term (P P,,)/(2), is the average value of the radial pressure gradient shown in FIG. 10.

Referring now to FIG. 12, there is shown a free body of the pressure sleeve 114; the enlarged annular portion 118 being shown in dashed outline, and the reduced diameter portion 117 being shown in solid outline. In summing forces, consideration will be given only to the sleeve portion 117, since insofar as the overall length of the pressure sleeve is concerned for this consideration, only the length L is of interest. The determination of the length L will be set forth below, but, it will be understood by reference'to the graph of FIG. 10, insofar as the provisions of the radial pressure P is concerned in regard to the length L, of the pressure sleeve, the only consideration is that it be sufficiently long to adequately provide the pressure P to the workpiece. Thus, the summation of forces acting on the solid outline portion of the free body pressure sleeve in FIG. 12, is expressed as follows:

where:

D, outside diameter of the pressure sleeve portion D inside diameter of the pressure sleeve portion 11 7 (assumed to be equal to the outside diameter D of the workpiece).

Referring again to equation (2) it will be understood that the expression to the left of the equal sign represents the forces acting to the right against the annular end of the sleeve portion 117, which forces are produced by the pressure P produced in the enlarged sleeve portion 118. The expressions to the right of the equal sign are the frictional forces acting to the left on the sleeve portion 117. Such forces are produced, respectively, by the workpiece acting against the interior surface of the sleeve portion 117, and the forcing member (FIG. 8) acting against the exterior surface of the sleeve portion 1 17. Thus for convenience in this equation, the coefficient of friction ft of the Teflon sleeve is used in both such last terms.

Inspection of equations (1) and (2) reveals two equations with two unknowns, i.e., lengths L and L it being understood that theaxial stress 8,, in equation l will be that pressure necessary to producethe required plastic state in the workpiece to form the desired flange 26, and which can be determined empirically. For example, as mentioned above, to produce a flange twice the diameter of the workpiece and nine (9) times the thickness of the workpiece, a satisfactory axial stress (S was 200,000 psi, when the copper workpiece had a yield strength of 10,000 psi. Further, it will be understood, that ideally the axial stress and the radial pressure along the length L will be equal.

With further regard to equation (1), the last two terms can be eliminated by letting length L, be assumed to be zero. The effect of such assumption is to state that the workpiece length L of FIG. 11 will be chosen such that the frictional forces F applied to workpiece length L, will alone be sufficient to force the workpiece into engagement with the die surface 158 with sufiicient force to produce the above-described plastic state in the workpiece. In view of the foregoing consideration with regard to equation (1), equation (1) can be solved for length L as follows:

Referring again to equation (2), equation (2) can be solved for length L by assuming a value for the outer diameter D, of the sleeve portion 11 which, ithas been determined, can be chosen primarily in accordance with choosinga thickness for the sleeve portion 117 which thickness permits ready machining, or otherwise forming, of the. pressure sleeve portion 117. In the same manner as set forth above with regard to equation (I), the term P is set, ideally, equal to the required axial stress S Hence, the only unknown term remaining in equation (2) is the length L which can be shown to be as follows:

Pm, 1mg L,

3 1.1), ft+ 51559 1.1m

Referring now to the above-mentioned consideration of whether the pressure sleeve portion 117 is to be of rectangular, or tapered, cross-sectional configuration, it will be understood that the technical considerations are the same; this is readily seen by inspection of equations l) and (2) by noting that the radial pressure used in the frictional force calculations involving the gradient portion of the radial pressure, is the average of such gradient, viz., (P P )/(2). Which average pressure is the pressure P,, of FIG. 13 in regard to the tapered sleeve portion 117 shown in solid outline. Thus it will be appreciated that the assumed outer diameter D for the rectangular sleeve portion 117 (shown in dashed outline in FIG. 13) will be the average thickness of the sleeve portion 117, when such sleeve portion is of tapered cross-sectional configuration as shown in FIG. 8. Hence, since L can be computed as shown above, and with the diameter D, assumed as taught above, the dimensions of the tapered sleeve portion are readily determined. The general considerations between whether such sleeve portion 117 should be tapered or rectangular, are: (1) that with the tapered configuration, the desired or required radial pressure gradient can be accomplished in a shorter length L than could be were such portion of rectangular configuration; and (2) that the rectangular configuration is more readily, and less expensively, produced.

Referring again to equations (1) and (2), it will be understood that the following assumptions were made: (1) the pressure sleeve 114 was fully loaded, or pressurized, by the forcing member 120, and (2) the mandrel was fully loaded, i.e., the workpiece 24 was in engagement with the die surface 158 with sufficient force to achieve the above-described plastic state in the workpiece.

While in the above discussion of the friction extrusion embodiment of the invention the radial pressure was applied to the workpiece by a solid member (pressure sleeve 114) to produce the required high frictional and high pressure engagement between the workpiece and the mandrel, it will be understood from reference to FIGS. 1, 2 and 3, that such high frictional and high pressure engagement between the workpiece and mandrel can be provided by a body of pressurized fluid which produces the forces 72 shown in FIG. 1. When a body of pressurized fluid is so utilized, it has been found that in some instances, the body of pressurized fluid provides the above-mentioned radial pressure required to achieve the high frictional and high pressure engagement between the workpiece and mandrel, and the primary forces which drive the workpiece through the die orifice and into engagement with the die surface, are the frictional forces applied to the workpiece by the advancing mandrel. It will be understood that in such instances, the above-mentioned considerations of workpiece pinch-off and buckling, and pressure gradient, are not present because the workpiece 24 is supported uniformly by the pressurized fluid, except of course, where the workpiece passes through the die orifice 22.

It will be manifest to those skilled in the art, that the foregoing is merely descriptive of the present invention and that many modifications and variations may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. The method of forming a flange on an end of a tubular member having an initial wall thickness, said method comprising:

a. placing a supporting member in operative supporting engagement with the entire inner periphery of said tubular member between a first station adjacent a die orifice and a second station upstream of the entrance end of said die orifice,

b. placing a closed and expandable chamber at the exit end of and communicating with the said die orifice, which chamber is expandable in a direction parallel to the longitudinal axis of the said die orifice,

. advancing said supporting member through said die orifice whereby by means of said operative engagement between said supporting member and the said inner periphery of said tubular member, the portion of said tubular member downstream of said second station is advanced through said die orifice into said closed chamber and against that wall of said closed chamber remote from said die orifice whereby said downstream portion of said tubular member is flared outwardly in said closed chamber, continuing the advance of said supporting member thereby to continue to advance said downstream portion of said tubular member into said closed chamber to fill said chamber and to pressurize that portion of said tubular member in said closed chamber whereby to place the said downstream portion of said tubular member in a state of increased deformability,

. upon said downstream portion of said tubular member within said closed chamber attaining said state of increased deformability, expanding said closed chamber in a direction parallel to the longitudinal axis of said die orifice as the advancement of said supporting member is continued,

f. whereby a flange is formed on the downstream portion of said tubular member, which flange has a thickness in a direction parallel to the longitudinal axis of said tubular member which is greater than the initial wall thickness of said tubular member.

2. Method of forming a flange on an end of a tubular member having an initial wall thickness according to claim 1, further including the steps of:

maintaining said downstream portion of said tubular member in said state of increased deformability during said forming of said flange.

3. Apparatus for forming a flange on an end of a tubular member having an initial wall thickness, comprismg:

a. a supporting member for insertion within said tubular member;

b. a die having a die orifice;

c. means providing a closed expandable chamber at the exit end of, and communicating with, said die orifice, said chamber being expandable in a direction parallel to the longitudinal axis of said die orifice;

d. means for placing said supporting member in operative supporting engagement with the entire periphery of said tubular member between a first station adjacent said die orifice and a second station upstream of the entrance end of said die orifice;

e. means for advancing said supporting member through said die orifice whereby by means of said operative engagement between said supporting member and the said inner periphery of said tubular member, the downstream portion of said tubular member is advanced through said die orifice into said closed chamber and against that wall of said closed chamber remote from said die orifice whereby said downstream portion of said tubular member is flared outwardly in said closed chamber,

f. said advancing means adapted to continue the advancement of said supporting member thereby to continue to advance said downstream portion of said tubular member into said closed chamber to fill said chamber and to pressurize that portion of said tubular member in said closed chamber whereby to place the said downstream portion of said tubular member in a state of increased deformability;

g. means for expanding said closed chamber in a direction parallel to said longitudinal axis of said die orifice upon said downstream portion of said tubular member within said closed chamber attaining said state of increased deformability as the advancement of said supporting member is continued;

h. whereby a flange is formed on the downstream portion of said tubular member, which flange has a thickness in a direction parallel to the longitudinal axis of said tubular member which is greater than the initial wall thickness of said tubular member.

4. Apparatus for forming a flange on the end of a tubular member having an initial wall thickness accord ing to claim 3, wherein said means for expanding said closed chamber is further adapted for cooperating with said supporting member and said chamber to maintain said downstream portion of said tubular member in said state of increased deformability during said forming of said flange.

5. Apparatus for forming a flange on an end of a tubular member, which comprises:

a mandrel complementary in shape to the interior of said tubular member and for supporting the interior of said tubular member;

a pressure vessel having a pressure chamber formed therein and for receiving fluid and said tubular member;

an extrusion die for permitting the forced passage therethrough of said mandrel supported tubular member, said extrusion die being complementary in shape to the exterior of said tubular member and being positioned at one end of said pressure chamber;

a movable back-up die positioned opposite said extrusion die and having a bore formed therein for 'receiving a portion of said mandrel;

a laterally movable annular member surrounding one end of said back-up die and for confining the outer diameter of said flange to be formed, said extrusion die, said back-up die and said annular member forming cooperatively a variable-sized die cavity of the desired shape of said flange to be formed; and

a piston extendable into said pressure chamber for raising the pressure in said fluid to a level sufficiently high to (i), apply hydrostatic pressure on said tubular member sufficiently high so as to place said member in a state of increased deformability, and (ii) to force said end of said tubular member, and successive portions thereof, while in said state, through said extrusion die and into said variable-sized die cavity to form said flange.

6. Apparatus according to claim 5 wherein said backup die is self-balancing so as to assist in achieving an even flow of said tubular member into all areas of said variable-sized die cavity, and which is comprised of:

a ball member in which said mandrel receiving bore is formed;

a socket member for receiving pivotably said ball member; and

said ball member, upon the occurrence of an uneven flow into an area of said die cavity, being pivotable in the direction of said area of uneven flow and effective, in cooperation with said mandrel, to tend to restore an even flow of said tubular member into all areas of said variable-sized die cavity.

7. Apparatus for forming a flange on a tubular member which comprises:

a pressure cylinder having a pressure chamber formed therein for receiving fluid;

an extrusion die for receiving successive portions of said tubular member and being provided with a centrally formed bore of a configuration substantially complementary to the exterior of said tubular member;

the entrance end of said extrusion die bore being slightly smaller than the exterior of said tubular member;

a mandrel positioned within said pressure chamber and insertable into said tubular member to provide internal support therefor;

the exterior of said mandrel being of a configuration substantially complementary to the interior of said tubular member and said mandrel being extendable through the extrusion die bore;

a back-up die positioned opposite said extrusion die and movable away therefrom;

an annular member encircling said back-up die and forming, in conjunction with said extrusion die and said back-up die, a variable-sized die cavity of a predeterminable ultimate size and shape substantially complementary to the size and shape of the flange to be formed on said tubular member;

a piston extendable into said pressure chamber for increasing the pressure in said fluid sufficiently such that said mandrel supported tubular member is forced through said extrusion die and into engagement with said back-up die to flare outwardly said tubular member into said die cavity;

said piston also for increasing the pressure in said fluid sufficiently such that said fluid pressure, in cooperation with said back-up die, (i) applies hydrostatic pressure on said tubular member, including said flared portion, sufficiently high such that said tubular member, including said flared portion, is in a state of increased deformability, and (ii) forces successively portions of said tubular member, in said state, through said extrusion die and into said variable-sized die cavity; and

said back-up die, in response to the extrusion of said tubular member thereinto, moves away from said extrusion die and increases the size of said variable-sized die cavity.

8. Apparatus for hydrostatically extruding a flange on an end of a metal tube, which comprises:

a mandrel insertable into said metal tube and for providing internal support to said metal tube;

a pressure vessel having a pressure chamber formed therein for receiving fluid and said mandrel supported metal tube;

an extrusion die positioned at one end of said pressure chamber and being provided with a centrally formed die orifice of a configuration substantially complementary to the outer cross-sectional dimension of said metal tube and for permitting the forced passage therethrough of said mandrel supported metal tube;

said extrusion die also including portions defining partially a die cavity;

a back-up die positioned opposite said extrusion die and including a die surface for defining partially said die cavity and for engagement by said end of said metal tube to flare said end outwardly into said cavity;

said back-up die having a centrally located, substantially frusto-conical shaped bore formed therein for receiving said mandrel upon the passage of said mandrel through said die orifice and said die cavit;

said back-up die being mounted for movement away from said extrusion die to provide for an increase in the size of said cavity;

an annular member closely surrounding one end of 35 said back-up die and for defining the balance of said die cavity;

said annular member being mounted for lateral movement to accommodate for varying wall thickness in said metal tube and for maintaining said mandrel in substantially central location of said bore formed in said back-up die; and

a piston insertable into said pressure chamber and for raising the pressure of said fluid to a level sufficiently high to (i) apply, in cooperation with said back-up die, hydrostatic pressure on said metal tube such that said metal tube is in a state of increased deformability, and (ii) force said mandrel supported metal tube through said die orifice to extrude portions of said metal tube into said die cavity, whereupon said back-up die (i) moves away from said extrusion die to increase the size of said die cavity, and (ii) maintains said extruded portions of said metal tube in close confinement so as to maintain, in cooperation with said fluid pressure, said metal tube in said state.

9. Apparatus according to claim 8 wherein said backup die is self-balancing and is comprised of:

orifice, in the direction of said excessive extrusion so as to reduce the distance between said mandrel and said extrusion die orifice in the direction of said excessive extrusion and retard the extrusion of said portions of said metal tube into said die cavity area.

10. Apparatus for extruding a flange on a tubular member, which comprises:

low friction means for engageably receiving said tubular member;

forcing means for receiving said low friction means and for forcing said low friction means into high pressure, low friction engagement with said tubular member;

high friction means insertable within said tubular member;

an extrusion die having an orifice formed therein;

means defining a die cavity;

means for operating said forcing means; and

means for operating said high friction means to pull frictionally said tubular member through said die orifice and extrude portions of said tubular member into said die cavity to form said flange.

11. Apparatus according to claim 10, wherein said low friction means, and said forcing means, are of such complementary configuration so as to develop a low friction, high pressure gradient between the low friction means and the tubular member.

12. Apparatus for extruding a flange on a tubular member, which comprises:

a mandrel insertable within said tubular member and for supporting the interior of said tubular member;

a low friction, pressure sleeve for encircling slidably said tubular member;

a forcing member engageable with said low friction pressure sleeve and for forcing said sleeve into pressed, low friction contact with said tubular member;

the exterior surface of said mandrel being such that the friction between said surface and the interior of said tubular member is greater than the friction between the exterior of the tubular member and said low friction, pressure sleeve;

an extrusion die having an extrusion die orifice formed therein for permitting the forced passage therethrough of said mandrel supported tubular member;

means defining an extrusion die cavity;

means forforcing said forcing member into engagement with said pressure sleeve to establish said pressed, low friction contact between said sleeve and said tubular member; and

means for forcing said mandrel, in said frictional contact with said tubular member, through said die orifice to pull frictionally said tubular member through said die orifice and extrude end portions thereof into said die cavity and form said flange.

13. Apparatus according to claim 13 wherein said low friction pressure sleeve and said forcing member are of complementary tapering configuration such that a pressure gradient is developed along the successive lengths of the tubular member encircled by said pressure sleeve, said pressure gradient being developed increasingly along said encircled length of tubular member as said pressure sleeve increases in width of taper.

14. Apparatus for forming a flange on an end of a tubular member, which comprises:

a mandrel insertable within said tubular member and for supporting the interior of said tubular member;

a low friction, pressure sleeve for encircling slidably said tubular member;

a forcing member engageable with said low friction, pressure sleeve and for forming said sleeve into pressed low friction contact with said tubular member;

the exterior surface of said mandrel being such that V the friction between said surface and the interior of said tubular member is greater than the friction between the exterior of the tubular member and said low friction, pressure sleeve;

an extrusion die having an extrusion die orifice formed therein for permitting the forced passage therethrough of said mandrel supported tubular member;

a back-up die;

means defining an expandable extrusion die cavity cooperatively with said extrusion die and said back-up die;

said mandrel for pulling frictionally said tubular member through said extrusion die orifice into said expandable die cavity;

said mandrel and said back-up die for cooperatively building up hydrostatic pressure in said tubular member sufficiently high so as to place said member in a plastic state and cause the extrusion of portions of said tubular member into said expandable die cavity; and

said back-up die being movable in response to said extrusion into said expandable die cavity to provide for an increase in the size of said die cavity and accommodate said portions of said tubular member extruded into said die cavity to form said flange.

15. The method of friction extrusion for extruding a flange on a deformable tubular member which comprises:

inserting a high friction mandrel into said tubular member;

surrounding said tubular member with a low friction sleeve;

forcing said low friction sleeve into high pressure,

low friction engagement with said ,tubular member;

applying force to said mandrel to frictionally move said tubular member through a die orifice and extrude portions of said tubular member into an expandable die cavity; including a back-up die, to form said flange; and

wherein said tubular member, by the cooperative effect of said mandrel and said back-up die, is pressurized to a degree sufficiently high to place said tubular member in a state of increased deformability.

16. The friction extrusion method of forming a flange on a deformable tubular member, which comprises the steps of:

inserting a high friction mandrel into said tubular member;

surrounding said tubular member with a low friction,

high pressure sleeve;

mechanically flaring the end of said tubular member; mechanically pressurizing said tubular member (including the flared end) to a degree sufficiently high so as to place said tubular member (including said flared end) in a state of increased deformability, by forcing said sleeve into low friction, high pressure engagement with said tubular member and by frictionally moving said tubular member with said mandrel through an extrusion die and into an expandable die cavity and into engagement with a back-up die; and

maintaining said tubular member, including said flared portion, in said state of increased deformability by the cooperative mechanical pressure applied by said sleeve, said mandrel and said back-up die, while moving successive portions of said tubular member through said extrusion die and into said expandable die cavity to cause the portion of said tubular member confined in said die cavity to increase in thickness beyond :said initial thickness and form a flange on said tubular member.

17. The friction extrusion method of forming a flange on an end of a tubular member, which comprises the steps of:

inserting a high friction mandrel into said tubular member;

surrounding said tubular member with a low friction,

high pressure sleeve;

flaring the end of said tubular member;

forcing said sleeve into low friction, high pressure engagement with said tubular member; and

while maintaining said sleeve in low friction, high pressure engagement with said tubular member, frictionally forcing portions of said tubular member with said mandrel through an extrusion die and into a die cavity to form a flange on said tubular member.

18. Method of deforming a workpiece against a die surface, which comprises:

positioning the workpiece between a high pressure,

low friction, solid member; and a high pressure, high friction drive member;

pressurizing said solid member to apply a normal pressure to the workpiece to force the workpiece into high pressure, high friction engagement with said drive member, and to apply a predetermined pressure gradient along the workpiece; and advancing said drive member to cause said member to frictionally transport said workpiece into engagement with said die surface with sufficient force to: (i) produce an axial stress in said workpiece sufficiently great to place said workpiece in a plastic state, and (ii) to deform said workpiece while in said plastic state; said normal pressure and said axial stress not departing; from each other at any point along the workpiece by an amount greater than the yield strength of the workpiece.

mg mum STATES PATENT OFFICE CERTIFICATE @F (IURRECTEUN Patent No 3 686, 910 Dated August 29, 1972 IWentor(s) FRANCIS JOSEPH FUCHS, JR.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

a- Column 2', line LE, "entirely" should read --entir ety-- .1

Column 3, line #5, "to" should read the- Column 8, lines 33-3 "comprises" should read --comprised-- Column 9, line 1, (after ll L insert -will Column 13, Equation 1, should read as follows s (p -(1 mg. (Pd fl'L )fm P+PO d'rr-L T [PDfl'L ft o Drrftl 2 Column 20, claim 13, "13' (second occurrence) should read -l2.

Signed and sealed this 23rd day of January 1973.

[SEAL] Attest:

EDWARD M-FLETCHER,JR. ROBERT GQTTSCHALK Attesting Officer Commissioner of Patents 

1. The method of forming a flange on an end of a tubular member having an initial wall thickness, said method comprising: a. placing a supporting member in operative supporting engagement with the entire Inner periphery of said tubular member between a first station adjacent a die orifice and a second station upstream of the entrance end of said die orifice, b. placing a closed and expandable chamber at the exit end of and communicating with the said die orifice, which chamber is expandable in a direction parallel to the longitudinal axis of the said die orifice, c. advancing said supporting member through said die orifice whereby by means of said operative engagement between said supporting member and the said inner periphery of said tubular member, the portion of said tubular member downstream of said second station is advanced through said die orifice into said closed chamber and against that wall of said closed chamber remote from said die orifice whereby said downstream portion of said tubular member is flared outwardly in said closed chamber, d. continuing the advance of said supporting member thereby to continue to advance said downstream portion of said tubular member into said closed chamber to fill said chamber and to pressurize that portion of said tubular member in said closed chamber whereby to place the said downstream portion of said tubular member in a state of increased deformability, e. upon said downstream portion of said tubular member within said closed chamber attaining said state of increased deformability, expanding said closed chamber in a direction parallel to the longitudinal axis of said die orifice as the advancement of said supporting member is continued, f. whereby a flange is formed on the downstream portion of said tubular member, which flange has a thickness in a direction parallel to the longitudinal axis of said tubular member which is greater than the initial wall thickness of said tubular member.
 2. Method of forming a flange on an end of a tubular member having an initial wall thickness according to claim 1, further including the steps of: maintaining said downstream portion of said tubular member in said state of increased deformability during said forming of said flange.
 3. Apparatus for forming a flange on an end of a tubular member having an initial wall thickness, comprising: a. a supporting member for insertion within said tubular member; b. a die having a die orifice; c. means providing a closed expandable chamber at the exit end of, and communicating with, said die orifice, said chamber being expandable in a direction parallel to the longitudinal axis of said die orifice; d. means for placing said supporting member in operative supporting engagement with the entire periphery of said tubular member between a first station adjacent said die orifice and a second station upstream of the entrance end of said die orifice; e. means for advancing said supporting member through said die orifice whereby by means of said operative engagement between said supporting member and the said inner periphery of said tubular member, the downstream portion of said tubular member is advanced through said die orifice into said closed chamber and against that wall of said closed chamber remote from said die orifice whereby said downstream portion of said tubular member is flared outwardly in said closed chamber, f. said advancing means adapted to continue the advancement of said supporting member thereby to continue to advance said downstream portion of said tubular member into said closed chamber to fill said chamber and to pressurize that portion of said tubular member in said closed chamber whereby to place the said downstream portion of said tubular member in a state of increased deformability; g. means for expanding said closed chamber in a direction parallel to said longitudinal axis of said die orifice upon said downstream portion of said tubular member within said closed chamber attaining said state of increased deformability as the advancement of said supporting member is continued; h. whereby a flange is formed on the downstream portion of said tubular member, which flange has a thickness in a direction parallel to the longitudinal axis of said tubular member which is greater than the initial wall thickness of said tubular member.
 4. Apparatus for forming a flange on the end of a tubular member having an initial wall thickness according to claim 3, wherein said means for expanding said closed chamber is further adapted for cooperating with said supporting member and said chamber to maintain said downstream portion of said tubular member in said state of increased deformability during said forming of said flange.
 5. Apparatus for forming a flange on an end of a tubular member, which comprises: a mandrel complementary in shape to the interior of said tubular member and for supporting the interior of said tubular member; a pressure vessel having a pressure chamber formed therein and for receiving fluid and said tubular member; an extrusion die for permitting the forced passage therethrough of said mandrel supported tubular member, said extrusion die being complementary in shape to the exterior of said tubular member and being positioned at one end of said pressure chamber; a movable back-up die positioned opposite said extrusion die and having a bore formed therein for receiving a portion of said mandrel; a laterally movable annular member surrounding one end of said back-up die and for confining the outer diameter of said flange to be formed, said extrusion die, said back-up die and said annular member forming cooperatively a variable-sized die cavity of the desired shape of said flange to be formed; and a piston extendable into said pressure chamber for raising the pressure in said fluid to a level sufficiently high to (i), apply hydrostatic pressure on said tubular member sufficiently high so as to place said member in a state of increased deformability, and (ii) to force said end of said tubular member, and successive portions thereof, while in said state, through said extrusion die and into said variable-sized die cavity to form said flange.
 6. Apparatus according to claim 5 wherein said back-up die is self-balancing so as to assist in achieving an even flow of said tubular member into all areas of said variable-sized die cavity, and which is comprised of: a ball member in which said mandrel receiving bore is formed; a socket member for receiving pivotably said ball member; and said ball member, upon the occurrence of an uneven flow into an area of said die cavity, being pivotable in the direction of said area of uneven flow and effective, in cooperation with said mandrel, to tend to restore an even flow of said tubular member into all areas of said variable-sized die cavity.
 7. Apparatus for forming a flange on a tubular member which comprises: a pressure cylinder having a pressure chamber formed therein for receiving fluid; an extrusion die for receiving successive portions of said tubular member and being provided with a centrally formed bore of a configuration substantially complementary to the exterior of said tubular member; the entrance end of said extrusion die bore being slightly smaller than the exterior of said tubular member; a mandrel positioned within said pressure chamber and insertable into said tubular member to provide internal support therefor; the exterior of said mandrel being of a configuration substantially complementary to the interior of said tubular member and said mandrel being extendable through the extrusion die bore; a back-up die positioned opposite said extrusion die and movable away therefrom; an annular member encircling said back-up die and forming, in conjunction with said extrusion die and said back-up die, a variable-sized die cavity of a predeterminable ultimate size and shape substantially complementary to the size and shape of the flange to be formed on said tubular member; a piston extendable into said pressure chamber for increasing the pressure in said fluid sufficiently such that said mandrel suppoRted tubular member is forced through said extrusion die and into engagement with said back-up die to flare outwardly said tubular member into said die cavity; said piston also for increasing the pressure in said fluid sufficiently such that said fluid pressure, in cooperation with said back-up die, (i) applies hydrostatic pressure on said tubular member, including said flared portion, sufficiently high such that said tubular member, including said flared portion, is in a state of increased deformability, and (ii) forces successively portions of said tubular member, in said state, through said extrusion die and into said variable-sized die cavity; and said back-up die, in response to the extrusion of said tubular member thereinto, moves away from said extrusion die and increases the size of said variable-sized die cavity.
 8. Apparatus for hydrostatically extruding a flange on an end of a metal tube, which comprises: a mandrel insertable into said metal tube and for providing internal support to said metal tube; a pressure vessel having a pressure chamber formed therein for receiving fluid and said mandrel supported metal tube; an extrusion die positioned at one end of said pressure chamber and being provided with a centrally formed die orifice of a configuration substantially complementary to the outer cross-sectional dimension of said metal tube and for permitting the forced passage therethrough of said mandrel supported metal tube; said extrusion die also including portions defining partially a die cavity; a back-up die positioned opposite said extrusion die and including a die surface for defining partially said die cavity and for engagement by said end of said metal tube to flare said end outwardly into said cavity; said back-up die having a centrally located, substantially frusto-conical shaped bore formed therein for receiving said mandrel upon the passage of said mandrel through said die orifice and said die cavity; said back-up die being mounted for movement away from said extrusion die to provide for an increase in the size of said cavity; an annular member closely surrounding one end of said back-up die and for defining the balance of said die cavity; said annular member being mounted for lateral movement to accommodate for varying wall thickness in said metal tube and for maintaining said mandrel in substantially central location of said bore formed in said back-up die; and a piston insertable into said pressure chamber and for raising the pressure of said fluid to a level sufficiently high to (i) apply, in cooperation with said back-up die, hydrostatic pressure on said metal tube such that said metal tube is in a state of increased deformability, and (ii) force said mandrel supported metal tube through said die orifice to extrude portions of said metal tube into said die cavity, whereupon said back-up die (i) moves away from said extrusion die to increase the size of said die cavity, and (ii) maintains said extruded portions of said metal tube in close confinement so as to maintain, in cooperation with said fluid pressure, said metal tube in said state.
 9. Apparatus according to claim 8 wherein said back-up die is self-balancing and is comprised of: a ball member on which said die surface is formed and in which said bore is formed; a socket member which receives pivotably said ball member; and said ball member, upon the occurrence of an excessive extrusion of said portions of said metal tube into an area of said die cavity, being pivotable in the direction of said die cavity area and effective to move said mandrel, within said extrusion die orifice, in the direction of said excessive extrusion so as to reduce the distance between said mandrel and said extrusion die orifice in the direction of said excessive extrusion and retard the extrusion of said portions of said metal tube into said die cavity area.
 10. Apparatus for extruding a flangE on a tubular member, which comprises: low friction means for engageably receiving said tubular member; forcing means for receiving said low friction means and for forcing said low friction means into high pressure, low friction engagement with said tubular member; high friction means insertable within said tubular member; an extrusion die having an orifice formed therein; means defining a die cavity; means for operating said forcing means; and means for operating said high friction means to pull frictionally said tubular member through said die orifice and extrude portions of said tubular member into said die cavity to form said flange.
 11. Apparatus according to claim 10, wherein said low friction means, and said forcing means, are of such complementary configuration so as to develop a low friction, high pressure gradient between the low friction means and the tubular member.
 12. Apparatus for extruding a flange on a tubular member, which comprises: a mandrel insertable within said tubular member and for supporting the interior of said tubular member; a low friction, pressure sleeve for encircling slidably said tubular member; a forcing member engageable with said low friction pressure sleeve and for forcing said sleeve into pressed, low friction contact with said tubular member; the exterior surface of said mandrel being such that the friction between said surface and the interior of said tubular member is greater than the friction between the exterior of the tubular member and said low friction, pressure sleeve; an extrusion die having an extrusion die orifice formed therein for permitting the forced passage therethrough of said mandrel supported tubular member; means defining an extrusion die cavity; means for forcing said forcing member into engagement with said pressure sleeve to establish said pressed, low friction contact between said sleeve and said tubular member; and means for forcing said mandrel, in said frictional contact with said tubular member, through said die orifice to pull frictionally said tubular member through said die orifice and extrude end portions thereof into said die cavity and form said flange.
 13. Apparatus according to claim 13 wherein said low friction pressure sleeve and said forcing member are of complementary tapering configuration such that a pressure gradient is developed along the successive lengths of the tubular member encircled by said pressure sleeve, said pressure gradient being developed increasingly along said encircled length of tubular member as said pressure sleeve increases in width of taper.
 14. Apparatus for forming a flange on an end of a tubular member, which comprises: a mandrel insertable within said tubular member and for supporting the interior of said tubular member; a low friction, pressure sleeve for encircling slidably said tubular member; a forcing member engageable with said low friction, pressure sleeve and for forming said sleeve into pressed low friction contact with said tubular member; the exterior surface of said mandrel being such that the friction between said surface and the interior of said tubular member is greater than the friction between the exterior of the tubular member and said low friction, pressure sleeve; an extrusion die having an extrusion die orifice formed therein for permitting the forced passage therethrough of said mandrel supported tubular member; a back-up die; means defining an expandable extrusion die cavity cooperatively with said extrusion die and said back-up die; said mandrel for pulling frictionally said tubular member through said extrusion die orifice into said expandable die cavity; said mandrel and said back-up die for cooperatively building up hydrostatic pressure in said tubular member sufficiently high so as to place said member in a plastic state and cause the extrusion of portions of said tubular member into said expandable die Cavity; and said back-up die being movable in response to said extrusion into said expandable die cavity to provide for an increase in the size of said die cavity and accommodate said portions of said tubular member extruded into said die cavity to form said flange.
 15. The method of friction extrusion for extruding a flange on a deformable tubular member which comprises: inserting a high friction mandrel into said tubular member; surrounding said tubular member with a low friction sleeve; forcing said low friction sleeve into high pressure, low friction engagement with said tubular member; applying force to said mandrel to frictionally move said tubular member through a die orifice and extrude portions of said tubular member into an expandable die cavity; including a back-up die, to form said flange; and wherein said tubular member, by the cooperative effect of said mandrel and said back-up die, is pressurized to a degree sufficiently high to place said tubular member in a state of increased deformability.
 16. The friction extrusion method of forming a flange on a deformable tubular member, which comprises the steps of: inserting a high friction mandrel into said tubular member; surrounding said tubular member with a low friction, high pressure sleeve; mechanically flaring the end of said tubular member; mechanically pressurizing said tubular member (including the flared end) to a degree sufficiently high so as to place said tubular member (including said flared end) in a state of increased deformability, by forcing said sleeve into low friction, high pressure engagement with said tubular member and by frictionally moving said tubular member with said mandrel through an extrusion die and into an expandable die cavity and into engagement with a back-up die; and maintaining said tubular member, including said flared portion, in said state of increased deformability by the cooperative mechanical pressure applied by said sleeve, said mandrel and said back-up die, while moving successive portions of said tubular member through said extrusion die and into said expandable die cavity to cause the portion of said tubular member confined in said die cavity to increase in thickness beyond said initial thickness and form a flange on said tubular member.
 17. The friction extrusion method of forming a flange on an end of a tubular member, which comprises the steps of: inserting a high friction mandrel into said tubular member; surrounding said tubular member with a low friction, high pressure sleeve; flaring the end of said tubular member; forcing said sleeve into low friction, high pressure engagement with said tubular member; and while maintaining said sleeve in low friction, high pressure engagement with said tubular member, frictionally forcing portions of said tubular member with said mandrel through an extrusion die and into a die cavity to form a flange on said tubular member.
 18. Method of deforming a workpiece against a die surface, which comprises: positioning the workpiece between a high pressure, low friction, solid member; and a high pressure, high friction drive member; pressurizing said solid member to apply a normal pressure to the workpiece to force the workpiece into high pressure, high friction engagement with said drive member, and to apply a predetermined pressure gradient along the workpiece; and advancing said drive member to cause said member to frictionally transport said workpiece into engagement with said die surface with sufficient force to: (i) produce an axial stress in said workpiece sufficiently great to place said workpiece in a plastic state, and (ii) to deform said workpiece while in said plastic state; said normal pressure and said axial stress not departing from each other at any point along the workpiece by an amount greater than the yield strength of the workpiece. 